﻿#region Copyright & License

//
// Author: Ian Davis <ian.f.davis@gmail.com> Copyright (c) 2007-2008, Ian Davs
//
// Portions of this software were developed for NUnit. See NOTICE.txt for more
// information. 
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
//

#endregion

#region Using Directives

using System;
using System.Collections;
using Ensurance.Properties;

#endregion

namespace Ensurance.Constraints.Collection
{
    public class CollectionEquivalentConstraint<T> : CollectionConstraint<T>
    {
        private IEnumerable Expected { get; set; }

        /// <summary>
        /// Construct a CollectionEquivalentConstraint
        /// </summary>
        /// <param name="expected"></param>
        public CollectionEquivalentConstraint( ICollection expected )
        {
            Expected = expected;
        }

        /// <summary>
        /// Test whether two collections are equivalent
        /// </summary>
        /// <param name="actual">The actual.</param>
        /// <returns></returns>
        protected override bool doMatch( ICollection actual )
        {
            // This is just an optimization
            if ( Expected is ICollection )
            {
                if ( actual.Count != ( (ICollection) Expected ).Count )
                {
                    return false;
                }
            }

            CollectionTally tally = new CollectionTally( Expected );
            return tally.CanRemove( actual ) && tally.AllCountsEqualTo( 0 );
        }

        /// <summary>
        /// Write a description of this constraint to a MessageWriter
        /// </summary>
        /// <param name="writer">The writer on which the description is displayed</param>
        /// <exception cref="ArgumentNullException">if the message writer is null.</exception>
        public override void WriteDescriptionTo( IMessageWriter writer )
        {
            if ( writer == null )
            {
                throw new ArgumentNullException( "writer" );
            }
            writer.WritePredicate( Resources.EquivalentTo );
            writer.WriteExpectedValue( Expected );
        }
    }
}